The present invention relates to an optical disk device configured to read data recorded on an optical disk such as a DVD (Digital Versatile Disk) or the like and record data on such an optical disk.
Optical disk devices have become widespread which are generally configured to read data recorded on an optical disk such as a DVD or the like and record data on such an optical disk.
The DVD is capable of recording not only motion picture and sound but also a variety of data. Recording modes adapted to the DVD include various modes such as a DVD-Video format (hereinafter will be referred to as Video mode) and a VR format (hereinafter will be referred to as VR mode).
The Video mode is a format originally made for DVD players for reproduction (ROM) only and hence has a high reproduction compatibility among existing DVD players. In the Video mode, data is recorded in a predetermined unit of cells. A cell consists of plural VOBUs (Video Object Unit). In such a VOBU, NV_PCK (Navigation Pack) is placed at the head and video and audio data (AV data) and like data as packed are inserted following NV_PCK.
However, since the Video mode is the format for reproduction only as described above, the Video mode has a drawback that it is difficult to record AV data in real time unlike the VR mode. The reason for this difficulty is that in newly recording AV data contained in a VOBU (to be referred to as current VOBU), information on other plural VOBUs to be recorded subsequently to the current VOBU has to be written to the current VOBU. Specifically, the Video mode requires that such information as the initial addresses of respective of the other plural VOBUs and the reproduction time of the cell and like information be written to the NV_PCK area in the current VOBU. For this reason, the other plural VOBUs to be reproduced subsequently to the current VOBU need be temporarily secured in semiconductor memory or the like in recording the current VOBU. This is one of the causes of the difficulty in real-time recording.
When the DVD is in a bad storage condition, the optical disk is subject to damage, stain and the like on its recording surface. If a certain degree of damage, stain or the like occurs on the recording surface of the optical disk, an error will result. Such an error makes it impossible to detect a target recording position, thus causing recording to be interrupted.
A conventional optical disk device is configured to carry out a recovery process for recovery from such an error thereby realizing stabilized recording on the DVD. The recovery process includes: performing a seek to find out an area allowing stabilized recording therein; determining whether or not the area sought is recordable; and resuming recording if the area is recordable.
Such a conventional optical disk device, however, involves the following problem associated with recording of real-time data such as a television program. That is, during a seek in the above-described recovery process, data is not recorded on the optical disk and, for this reason, all data inputted in real time is temporarily stored in semiconductor memory. Accordingly, the amount of data accumulated in the semiconductor memory increases during the seek. When the amount of accumulated data exceeds the maximum memory capacity, data inputted thereafter in real time overwrites the data in the memory. As a result, the data in the memory (data not yet recorded on the optical disk) is lost, which raises a data break-off problem (buffer overflow). In order to avoid this problem, the capacity of the semiconductor memory needs to be increased to such an extent as to obviate overwriting of data unrecorded on the optical disk by data inputted in real time.
In attempt to solve this problem, an optical disk device as described in Japanese Patent Laid-Open Publication No. 2001-243698 has been proposed.
This optical disk device has a recording rate of data to be recorded on the optical disk that is set higher than an input rate of data to be inputted to the semiconductor memory. For this reason, usually, data inputted to the semiconductor memory is immediately recorded on the optical disk. This optical disk device is configured to perform a seek upon occurrence of an error and set the input rate to a lower value than the usual input rate at the time the amount of data accumulated in the semiconductor memory reaches a fixed amount during the seek.
However, the optical disk device described in the above-noted Japanese Patent Laid-Open Publication No. 2001-243698 is made without any consideration of Video mode recording. For example, when an error occurs, the optical disk device performs a seek to resume recording; however, a problem arises when an error occurs after NV_PCK has been recorded on the optical disk. Specifically, in NV_PCK recorded on the optical disk there are written the initial addresses of respective of the aforementioned other plural VOBUs as already fixed ones and, hence, these initial addresses cannot be changed any longer. If the optical disk device performs a seek by force to resume recording in disregard of that fact, data recorded cannot be reproduced correctly.
Accordingly, it is an object of the present invention to provide an optical disk device capable of realizing stabilized recording on the DVD even when an error occurs during recording in the Video mode.